This is important because ilvl is used to determine which affixes (prefix and suffix) can appear on a magic item. Every affix has a minimum ilvl: if the base item is not ranked highly enough, the affix simply cannot appear. (This helps to prevent Quill Rats from dropping Valkyrie's Amulet, requiring level 67 to equip).

Independently of the formula above, the new amulet will have one suffix, one prefix, or one of each according to these probabilities:
50% Suffix Only
25% Prefix Only
25% Both
That translates to a 1-in-4 odds of rolling a 2-modifier item - you know, the good stuff : )

This recipe is interesting for two reasons: first, the item level of the input jewelry is unimportant: the only thing that matters is the level of your character. So, gather up every crap magic ring and amulet you run across, and hang on to it for your high level to craft with. Failed crafting attempts can also be recycled into the next recipe, making this a very convenient and easy way to produce some useful items.
It is also interesting because there are no additional ingredients. You don't have to hunt down gems or jewels or runes or whatever. Just chuck in three rings and go.

Rare, unique, set jewelry can't be used in this recipe.

Where do I get materials for crafting?
Lots of monsters have the ability to drop jewelry, so many will spawn in a longer game. Many players ignore blue rings and amulets in a game, or quickly ID and then drop them back on the ground. You should be able to scavenge quite a lot of rings this way.

If a player grabs your ring and doesn't drop it, follow him back to town next time. He's likely to ID it, disapprove, then sell it to a merchant. You can simply buy it back for yourself. If it didn't carry charges it's probably cheap.

Best locations for finding rings are well-known: Andariel in Norm, NM, also the Summoner and then other act bosses are commonly farmed. Go SOJ hunting and just keep every ring you find.

What can I get with this?
Use the tables below: choose one Prefix, and one Suffix.

Prefixes
[TABLE="class: grid, width: 500"]
<tbody>

Type

Affix Name

Value

Affix Lvl

MIN CLVL TO ROLL

+ AR

Bronze

10-20

1

2

% Dmg to Mana

Vulpine

7-12

9

12

+ Mana

Lizard's

3-5

3

4

Snake's

6-10

6

8

Serpent's

11-20

14

9

Drake's

21-30

20

27

Dragon's

31-40

24

32

Wyrm's

41-60

30

40

Great Wyrm's

61-90

37

50

Bahamut's

91-120

45

60

+ Stamina

Rugged

5-10

1

2

Rugged

11-20

8

11

+ Fire Res

Crimson

5-10

5

7

Russet

11-20

12

16

Garnet

21-30

18

24

Ruby

31-40

25

34

+ Cold Res

Azure

5-10

5

7

Lapis

11-20

12

16

Cobalt

21-30

18

24

Sapphire

31-40

25

34

+ Lit Res

Tangerine

5-10

5

7

Ocher

11-20

12

16

Coral

21-30

18

24

Amber

31-40

25

34

+ Poison Res

Beryl

5-10

5

7

Viridian

11-20

12

16

Jade

21-30

18

24

Emerald

31-40

25

34

+ Res All

Shimmering

3-7

8

11

Rainbow

8-11

21

28

Scintillating

12-15

34

46

Prismatic

16-20

42

56

Chromatic

21-30

55

74

+ Class Skills

Maiden's

+1 All Zon

36

48

Magekiller's

+1 Assassin

36

48

Slayer's

+1 Barb

36

48

Shaman's

+1 Druid

36

48

Monk's

+1 Pally

36

48

Summoner's

+1 Necro

36

48

Angel's

+1 Sorc

36

48

+ Skilltree

Acrobatic

+1 Zon Passive

20

27

Gymnastic

+2 ...

40

54

Athletic

+3 ...

60

80

Entrapping

+1 Traps

20

27

Trickster's

+2 ...

40

54

Cunning

+3 ...

60

80

Mentalist's

+1 Shadow Disciplines

20

27

Psychic

+2 ...

40

54

Shadow

+3 ...

60

80

Shogukusha's

+1 Martial Arts

20

27

Sensei's

+2 ...

40

54

Kenshi's

+3 ...

60

80

Expert's

+1 Combat Skills

20

27

Veteran's

+2 ...

40

54

Master's

+3 ...

60

80

Fanatic

+1 Combat Masteries

20

27

Raging

+2 ...

40

54

Furious

+3 ...

60

80

Sounding

+1 Warcries

20

27

Resonant

+2 ...

40

54

Echoing

+3 ...

60

80

Trainer's

+1 Druid Summoning

20

27

Caretaker's

+2 ...

40

54

Keeper's

+3 ...

60

80

Spiritual

+1 Shapeshifting

20

27

Feral

+2 ...

40

54

Communal

+3 ...

60

80

Natural

+1 Elemental

20

27

Terrene

+2 ...

40

54

Gaean

+3 ...

60

80

Hexing

+1 Curses

20

27

Blighting

+2 ...

40

54

Cursing

+3 ...

60

80

Fungal

+1 Poison / Bone

20

27

Noxious

+2 ...

40

54

Venomous

+3 ...

60

80

Graverobber's

+1 Necro Summoning

20

27

Mojo

+2 ...

40

54

Golemlord's

+3 ...

60

80

Lion Branded

+1 Pally Combat Skills

20

27

Hawk Branded

+2 ...

40

54

Rose Branded

+3 ...

60

80

Captain's

+1 Offensive Aura

20

27

Commander's

+2 ...

40

54

Marshal's

+3 ...

60

80

Preserver's

+1 Defensive Aura

20

27

Warden's

+2 ...

40

54

Guardian's

+3 ...

60

80

Burning

+1 Fire

20

27

Blazing

+2 ...

40

54

Volcanic

+3 ...

60

80

Sparking

+1 Lightning

20

27

Charged

+2 ...

40

54

Powered

+3 ...

60

80

Chilling

+1 Ice

20

27

Freezing

+2 ...

40

54

Glacial

+3 ...

60

80

+ % MF

Felicitous

5-10

5

7

Fortuitous

11-15

12

16

+ Light Rad

Glimmering

1

1

2

Glowing

2

6

8

</tbody>[/TABLE]

Suffixes
[TABLE="class: grid, width: 500"]
<tbody>

Type

Affix Name

Value

Affix Lvl

MIN CLVL TO ROLL

+ Str

Strength

1-2

1

2

Might

3-5

10

14

Ox

6-10

26

35

Giant

11-15

42

56

Titan

16-20

58

78

Atlas

21-30

71

95

+ Dex

Dexterity

1-2

1

2

Skill

3-5

11

15

Accuracy

6-10

27

36

Precision

11-15

43

58

Perfection

16-20

59

79

Nirvana

21-30

73

96

+ Min Dmg

Worth

2-3

15

20

Measure

4-5

37

50

Excellence

6-9

59

79

+ Max Dmg

Craftsmanship

1

1

2

Maiming

3-4

42

56

+ Cold Dmg

Frost

1-(3-6), 2sec

55

74

+ Fire Dmg

Flame

1-(2-6)

40

54

+ Lit Dmg

Shock

1-(11-23)

50

67

+ Poison Dmg

Blight

50 over 3sec

45

60

Faster Cast Rate

Apprentice

10%

5

7

+ Life

Jackal

1-5

1

2

Fox

6-10

7

10

Wolf

11-20

15

20

Tiger

21-30

20

27

Mammoth

31-40

25

34

Colossus

41-60

30

40

Squid

61-80

40

54

Whale

81-100

50

67

+Life /Clvl

Centaur

.75/lvl

1

2

+ Energy

Energy

1-3

1

2

Mind

4-6

7

10

Brilliance

7-10

13

18

Sorcery

11-15

21

28

Wizardry

16-20

31

42

Enlightenment

21-30

41

55

+Mana/Clvl

Memory

.75/lvl

20

27

Replenish Life

Regeneration

3-5

10

14

Regrowth

6-10

17

23

Revivification

11-15

38

51

% Life Leech

Leech

2-3

24

32

Locust

4-5

57

76

% Mana Leech

Bat

3-4

15

20

Wraith

5-6

58

78

Damage Reduce

Health

1

7

10

Protection

2

18

24

Absorption

3

26

35

Life

4

35

47

Life Everlasting

10-25

45

60

Magic DmgReduce

Warding

1

7

10

Sentinel

2

18

24

Guarding

3

26

35

Negation

4-6

42

56

Poison Length Reduce

Remedy

25%

7

10

Amelioration

50%

18

24

Defiance

75%

25

34

Freeze Duration

Thawing

50%

10

14

+ Light Radius, + AR

Light

1 / 15

6

8

Radiance

3 / 30

15

20

Sun

5 / 5%

17

23

+ % MF

Chance

5-15

12

16

Fortune

16-25

16

22

Luck

26-35

26

35

+ % Gold Find

Greed

25-40

1

2

Wealth

41-80

17

23

% Chance to Cast
When Struck

Charged Bolt

10% / lvl3

6

8

Charged Bolt

12% / lvl4

16

22

Charged Bolt

14% / lvl5

26

35

Frost Shield

5% / lvl3

12

16

Hydra Shield

10% / lvl3

40

54

% Chance to Cast
On Attack

Chain Lightning

5% / lvl3

25

34

Chain Lightning

8% / lvl3

35

47

Chain Lightning

8% / lvl5

45

60

Charges

Attract

lvl1 / 22ch

60

80

Bone Spirit

lvl1 / 22ch

72

96

Frost Nova

lvl2 / 25ch

24

32

Frost Nova

lvl3 / 27ch

24

32

Grim Ward

lvl1 / 22ch

60

80

Holy Bolt

lvl3 / 27ch

24

32

Holy Bolt

lvl4 / 30ch

24

32

Holy Bolt

lvl5 / 32ch

24

32

Inner Sight

lvl3 / 41ch

18

24

Inner Sight

lvl4 / 45ch

18

24

Inner Sight

lvl5 / 48ch

18

24

Teleportation

lvl1 / 22ch

48

64

Teleportation

lvl2 / 25ch

48

64

Tornado

lvl1 / 22ch

60

80

Twister

lvl1 / 22ch

48

64

</tbody>[/TABLE]

What can I not get with this?
Because maximum ilvl of amulets generated with this recipe is 74 (using a level 99 character), some affixes will be excluded from the list. Here is a table showing affixes which cannot be crafted using this recipe.

PrefixAny +2 to All Class Skills Prefix (ilvl 90)

Valkyrie's: +2 to Zon Skills

Witch-hunter's: +2 to Assassin Skills

Berserker's: +2 to Barbarian Skills

Hierophant's: +2 to Druid Skills

Priest's: +2 to Pally Skills

Necromancer's: +2 to Necro Skills

Arch-Angel's: +2 to Sorc Skills

Suffix
[TABLE="class: grid, width: 500"]
<tbody>

Performance

+10-13 to Min Dmg

ilvl 81

Lamprey

7-8% Life Leech

ilvl 85

Vampire

6% Mana Leech

ilvl 78

</tbody>[/TABLE]

Okay, but what do I actually WANT to get?
First, you want an item with _both_ prefix and suffix. Multi-affix does not increase the required "to equip" level - it simply uses the higher of the two affixes - so shoot for two when you can get it, there are no drawbacks aside from the 25% odds to get it.

Next... Of the available prefixes, these are the most valuable:

Bahamut's (+91-120 Mana)

Chromatic (+21-30 Resist All)

Fortuitous (+11-15% MF)

Any of the +3 to Skill Tree mods

Lesser valued suffixes could be perfect single-element resists, or the +1 all class skills mods, but only if combined with a good suffix.

Ruby (+31-40 Resist Fire)

Sapphire (+31-40 Resist Cold)

Amber (+31-40 Resist Lightning)

Emerald (+31-40 Resist Poison)

Any of the +1 to Class Skills mods

Next, the list of most valued suffixes:

Atlas (+21-30 Str)

Nirvana (+21-30 Dex)

Apprentice (10% FCR)

Whale (+81-100 Life)

Enlightenment (+21-30 Energy)

Life Everlasting (10-25 Damage Reduction) < only useful for certain specialized builds, and only if near-perfect

Luck (+26-35% MF)

Lesser valued suffixes are these second-tier affixes, where the best version can't be crafted - only gambled or dropped.

Pretty much any combination of Good Prefix + Good Suffix makes for a very nice ring. Exceptions would be useless cross-affixes, like an Angel's Amulet of the Locust - adding Life Leech to caster rings is pointless.

With a possible total of +50% Magic Find on a maxed amulet such as this, do I need to say more? Easily rivals unique amulets depending on how you play your character and how much you're into Magic Find items. Chromatic Amulet of the Whale
+21-30% to each Resistance / +81-100 to Life

Maxed stats of +30% to all resists and +100 to Life is certainly nothing to laugh at. Even this amulet with average stats (+25% Resist All / +90 Life) would be very good. I'm sure many hardcore characters would be interested in this one.

Bahamut's Amulet of Enlightenment+91-120 to Mana / +21-30 to Energy

A lesser Frostburn around your neck, especially when close to max numbers.

What level should I use to craft?
There are two approaches to take here.

The first: simply use your highest level to roll everything and see what comes out. The advantage is that high levels have access to a wide array of affixes, making all combinations available. The disadvantage is that there is a bit of crap available with high ilvl requirements (Attract, Bone Spirit, Grim Ward and Tornado Charges, + to Min / Max / Poison / Fire / Lightning damage (all too low damage to be useful), Replenish Life (too slow to be useful), and the Chain Lightning on Attack / Nova when Hit) which you could potentially roll as well. Carefully inspecting your level first may give you the best chance.

The second: pick what you want, and use a character whose level ranges from (min CLVL to roll) to (min CLVL to roll next highest affix, -1). This deserves an example:
Suppose you're gunning for a Fortuitous Amulet of Luck. Checking the table, we see the minimum CLVL to roll Fortuitous is 16, while the min to roll Of Fortune is 35. So we need at least a level 35 character to get it.
The next CLVL TO ROLL after 35 is 36: "Accuracy" becomes available to roll. If you try to roll amulets with a level 36+ character, you're making (at least) this additional affix available, which dilutes the pool a bit and makes it harder to get exactly what you want. You should thus roll for Fortuitous Ring of Fortune with a character level 35 for the greatest chance of success.

To do: Specific recommendations, like the Rings guide.

I have a question that wasn't answered here.
Post below, someone should be able to help you.

It would be interesting if you added some odds to roll certain jewels to give an indication. for example at lvl 35 the chance to roll a fort amulet of luck is 2/9261, so you will need at average 13800 rings to make 1 fortuitous amulet of luck.
Also you might want to ctrl-f your guide for the word "ring" sometimes you accidently say ring, while you are talking about amulet.

Personally I think it is a waste of time to craft or even identify magic amulets when playing twinked, however in untwinked single pass tournies it is common to end up using magic amulets and rolling them at certain lvls can be a smart way. waiting for lvl 35/56/60/74 for luck/prismatic/+3skills/chromatic.